1. Technical Field
The present invention relates to freeze detecting devices for an active shutter of a vehicle, which detects freezing of an active shutter.
2. Related Art
As is widely known, in a vehicle such as an automobile, travelling wind (cooling air) is directed into the moving vehicle through an opening formed on a front bumper, a front grill or the like provided on the front of the vehicle. The travelling wind that is brought in is guided to a heat exchanger such as a radiator and a condenser for an air conditioning device provided on the front of an engine compartment to cool them.
When the travelling wind is guided into the engine compartment through the heat exchanger, the wind causes turbulent flow in the engine compartment and increases air resistance, thereby leading to poor fuel economy. Therefore, it is desirable for the travelling wind that passes through the heat exchanger to be the minimal amount.
As a technique to control the travelling wind that passes through the heat exchanger, for example, a technique to control the amount of travelling wind that passes through is disclosed in Japanese Unexamined Patent Application Publication 2007-1503, in which an active shutter is provided between the front grill and the heat exchanger, and the active shutter is opened and closed with a shutter control device according to the vehicle speed and the temperature of cooling water and so forth.
By using this shutter control device, when the engine temperature is low in a cold environment such as in winter, the active shutter is fully closed and the travelling wind that passes through the heat exchanger is reduced, ambient temperature fall in the engine compartment is suppressed, and heat loss from auxiliary equipment such as the engine, an oil pan, an alternator, a compressor, and the like can be suppressed. Further, by fully closing the active shutter, the travelling wind guided into the engine compartment is reduced, the occurrence of turbulent flow in the engine compartment is suppressed and air resistance is reduced, whereby fuel efficiency can be improved.
On the other hand, when the travelling wind temperature is high and the engine temperature is relatively high in a hot environment such as in summertime, the active shutter is fully opened and the travelling wind is actively taken into the engine compartment to cool the heat exchangers, while the various devices such as the engine, oil pan, alternator, compressor and the like are cooled as done in the normal condition, whereby heat damage can be suppressed.
In the case that the external air temperature is lower than the temperature at which freezing starts (freezing temperature) (hereinafter referred to as a “low external air temperature”), the above-mentioned shutter control device fully closes off the active shutter so as to inhibit excessive cooling in the engine compartment and to quickly increase the internal temperature.
However, in the case that high load driving state is continuous, such as high load driving at a low speed or continuously driving up a hill, the engine temperature and transmission temperature readily increases even during the driving when the external air temperature is low. Accordingly, in order to inhibit heat damage by the increase in temperature in the engine compartment, in the case that the temperature in the engine compartment exceeds a predetermined threshold, the shutter control device opens the active shutter even during driving when the external air temperature is low.
However, the active shutter is easy to freeze during the driving when the external air temperature is low, and where even if a driving signal to open an actuator provided to the active shutter is output from the shutter control device, the active shutter sometimes does not open. If the driver continues high load driving without noticing that the active shutter is frozen, the engine compartment will constantly maintain a high temperature, components made from rubber or resin that are disposed in the periphery of the heat source such as the engine or transmission may incur heat damage, aging degradation may advance, and life-span may be shortened.